This application claims priority to Korean Patent Application 10-2003-58525, filed Aug. 23, 2003, which is incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a norbornene monomer, an acrylate monomer and a methacrylate monomer containing an oxepan-2-one group, and methods for preparing the monomers. In some embodiments, the present invention relates to a norbornene monomer, an acrylate monomer and a methacrylate monomer containing a novel oxepan-2-one group which can be used to prepare photoresist compositions, and methods for preparing the monomers.
The present invention also relates to photoresist compositions and methods for preparing the photoresist compositions. The present invention relates to a photoresist composition comprising a polymer prepared by homopolymerizing a monomer selected from norbornene, acrylate and methacrylate monomers, or copolymerizing the monomer with another monomer. The photoresist composition makes it possible to form high-resolution patterns even in the far ultraviolet region:
The present invention also relates to methods for forming patterns using the photoresist compositions.
2. Description of the Related Art
In recent years, in order to attain high sensitivity in fine fabrication technology for production of semiconductor devices, special attention has been paid to chemically amplified photoresists suitable for lithography using a light source in the far ultraviolet region, such as a KrF excimer laser (248 nm), an ArF excimer laser (193 nm) or an F2 excimer laser (157 nm). These photoresists are typically fabricated by blending a photoacid generator, an acid labile photoresist polymer, a dissolution inhibitor, etc.
In general, upon exposure of the chemically amplified photoresists to light, a large variation in the polarity of the dissolution inhibitor bonded to the polymer backbone is caused by the catalytic action of an acid generated from the photoacid generator. The development of the photoresist with a polar or non-polar solvent leads to the formation of positive- or negative-type photosensitive patterns.
Copolymers consisting of norbornene and maleic anhydride (COMA), methacrylate copolymers developed by Fujitsu Ltd., Japan (U.S. Pat. No. 5,968,713), copolymers consisting of vinylether and maleic anhydride (VEMA) developed by Samsung Electronics, Korea, and ROMA-type copolymers developed by Kumho, Korea, are examples of representative chemically amplified photoresist polymers for an ArF excimer laser.
These copolymers use esters of tert-butyl, acetals of ethoxyethyl, ketals, etc., as carboxylprotecting groups. However, these protecting groups release low molecular weight organic substances such as isobutene, ethyl vinyl ether, acetaldehyde and ethanol as byproducts due to photogenerated acids upon exposure and post-exposure bake.
The released low molecular weight organic substances are readily volatile, causing a change in the volume of the photoresist film and forming an organic film on the lens surface of an exposure device. The organic film formation lowers the transmittance of the lens and thus results in low productivity of the photoresist and pattern deformation (Hien, S., et al., Francis M. Houlihan, Ed., Proceedings of SPIE, Vol. 4345, p 439, 26th International Symposium on Microlithography, Santa Clara, Calif. (2001)).
Thus, there is a need for novel chemically amplified photoresists without volatilization of any chemical substances from photoresist polymers in the course of lithographic processes.